296 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



would be written CuO and CuO 2 , but as the molecules of 

 the two compounds are now regarded as containing only a 

 single atom of oxygen the formulae are actually written as 

 Cu. 2 O and CuO. 



Berzelius gave a list of fifty elements, with corresponding 

 symbols. The majority of the symbols are easily-recognised 

 abbreviations ; exceptions are found in the case of : 



Gold Aurum Au 



Silver Argentum Ag 



Copper Cuprum Cu 



Iron Ferrum Fe 



Lead Plumbum Pb 



Tin Stannum Sn 



Mercury Hydrargyrum Hg 



Antimony Stibium Sb 



Sodium Natrium Na 



Potassium Kalium K 



The number of recognised elements has now grown to 

 over 80. 



The laws of chemical combination explained by the 

 atomic theory. One of the chief merits of Dalton's atomic 

 theory was that it afforded a simple and obvious explanation 

 of the three chief laws of chemical combination, namely : 



(1) The law of fixed proportions. 



(2) The law of multiple proportions. 



(3) The law of reciprocal proportions. 



B. FIXED PROPORTIONS. 



The law of fixed proportions. Throughout the alche- 

 mistic period very little attention was paid to the weights of 

 the substances obtained in chemical processes. The study 

 of chemical composition was confined to qualitative 

 experiments, designed to find out the nature and not the 



